Method and apparatus for the optimum blending of lubricating base oils and an additive

ABSTRACT

A method and apparatus for enabling the computation of a minimum cost blend of lubricating oil base stocks, wherein a viscosity index improver additive is included. System includes measurement of viscosity and related data at two separate concentrations of the additive where such concentrations are in the range from about 1 percent to about 10 percent of the additive with a given base oil. Data obtained are used in non-linear formulae to provide bases for calculating optimum blends to obtain particular specifications with minimum cost.

United States Patent Leonard et al.

[11] 3,826,904 [451 July 30,1974

Inventors:

METHOD AND APPARATUS FOR THE OPTIMUM BLENDING OF LUBRICATING BASE OILS AND AN ADDITIVE John M. Leonard, Houston, Tex.; John S. Lewis, Jr., Huntsville, Ala

Texaco Inc., New York, NY.

Filed: Oct. 4, 1972 Appl. No.: 295,060

Related US. Application Data Continuation of Ser. No. 90,244, Nov. 17, 1970, abandoned.

Assignee:

U.S. Cl...... 235/l l.1, 235/151.l2, 208/DIG.

Int. Cl... G0ln /46,'F23m 5/00, G06p 15/46 Field of Search 235/151.1, 151.12; 444/1; 252/59, R; 208/DlG. 1

References Cited UNlTED STATES PATENTS 4/1964 Stoutetal. ..235/'151.12x 9/1967 McEvoy ...235/151.12x

BLENDlNG TANK 1 3,484,590 12/1969 Stanton 235/151.12 3,582,281 6/1971 Fenske et al 208/DlG. 1 3,590,227 6/1971 Porter et al 235/151 .12 3,666,931 5/1972 Woodle 208/DIG. 1 X 3,725,653 4/1973 Carr et a1 208/D1G. l X

Primary Examiner-Ma1colm A. Morrison Assistant ExaminerEdward J. Wise Attorney, Agent, or Firm-Thomas H. Whaley; C. G. Ries [5 7] ABSTRACT A method and apparatus'for enabling the computation of a minimum cost blend of lubiicgtling oil base stocks, wherein a viscosity index impr ver additive is included. System includes measurement of viscosity and related data at two separate concentrations of the additive where such concentrations are in the range from about 1 percent to about 10 percent of the additive with a given base oil. Data obtained are used in nonlinear formulae to provide bases for calculating optimum blends to obtain particular specifications with minimum cost.

3 Claims, 9 Drawing Figures BASE on. A

1 BASE OIL C 1 |o l "EIOC xa i 2 p BLENDING SIGNAL CONTROL GRAiMMER MEANS 14 MEANS 14A 1i -53. V l l -2B ear/ Lt l. CONSTRAINT -42 ac was PAIENIEBJMOIW 3.826.904

sum 3 or 5 m V Y X AIP.

N ETWORK FIG, 6

Hf, NETWORK 55 BLENDING OF LUBRICATING BASE OILS AND AN ADDITIVE CROSS REFERENCE TQ RELATED APPLICATIONS This application is a continuation asto all subject matter common to US. application, Ser. No. 90,244, now abandoned,'filed Nov. 17, 1970 by John M. Leonard et al., and assigned to Texaco Inc., assignee of the present invention, and a continuation-in-part for all additional subject matter.

BACKGROUNDAOF THE INVENTION found that. where such blends included therein one of I more viscosity index improvement-type additives, the resulting blend was not predictable. Thus, it was found that additives of the sort mentioned could not be blended on the basis of a predetermined viscosity index for the additive, since the I-l-value would vary in a non-linear manner with the amount of additive and the particular .base oil with which it was blended. Pour points also varied non-linearly with the amount of additive and the base oil used.

Consequently, it is an object of this invention to provide a method and system for predetermining a particular blend of base oils with a viscosity index improver additive, so as to provide predetermined characteristics for the resulting blend.

SUMMARY OF THE INVENTION A system controls the blending of base oils and an additive to achieve a desired blend oil having predetermined characteristics at minimum cost. The system includes apparatus which controls the quantities of base oils and additive being provided to a blending tank in accordance with control signals. A circuit provides signals corresponding to the predetermined characteristics to a network. The network provides the control signails to the apparatus in accordance with thecharacteristic signals. a I

The objects and advantages ofthe invention will appear hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein two embodiments of the invention are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes'only and are not to be construed as defining the limits of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a simplified block diagram of a control system, constructed in accordance with the present invention, controlling apparatus shown in schematic form, for the blending of base oils with an additive.

FIGS. 2, 3, 4 and 7 are detailed block diagrams of the programmer, the x,- signal means, the constraint control means and the blending control means, respectively, shown in FIG. 1.

FIGS. 5 and 6 are detailed block diagrams of the H network and the BV, network, respectively.

FIG. 8 shows another embodiment of the present invention in which a general purpose digital computer is used to control the blending of base oils with an additive.

FIG. 9 is a non-linear graph illustrating the non-linear relationship of a base oil mixture and the percentage of additive in the mixture.

DESCRIPTION OF THE PREFERRED} EMBODIMENTS Lubricating oils are often blended in order to meet predetermined specifications, e.g., those called for to meet a. customers desires. Heretofore, that could be accomplished in a straightforward mann'er'sincethe characteristics of the blend varied in proportion with the volume-fraction of the base oils of the blend. How- 3 ever, it was found that the addition of a viscosity index additive could not be defined.

improver additive created conditions such that the linear blending of the base stocks of lubricating oils could no longer be carried out with an expectation of providing a predetermined blend viscosity or viscosity. index. It was found that the viscosity index improveradditive did not act as a: lubricating oil in that its own viscosity H-value was nota constant but varied according to the 1 base oil or oils in the blend. It was also discovered that the pour point depressant effects of the VI improver additive varied according to the base oil or oils in the blend. Thus, a relationshipbetween the viscosity and pour point of a blend of base oils and the viscosity and pour point of that blend with a viscosity index improver It maybe noted that the above-mentioned l-I-valuef is an element in theformula for calculating the viscosity index of any given oil. The formula is given and explained in the Standard Method for Calculating Viscosity Index from Kinematic Viscosity of the American Society for Testing and Materials under the fixed designation D2270. Such Standard is published by the Society with an annual issue.-

Another approach tothe problem was to assume. a constant H-value for a particular additive over a limited range of viscosity of a base oil-blend. However, this was found not to work since it appeared that the effect of the additive on the viscosity of several different base oil blends, each of which blends had the sameviscosity, indicated that the assumed or pseudo-H-values were not usable. V

It was discovered that if the viscosities of a particular lubricating oil base stock at standard temperatures, e.g., F and 210F, were measured undertwo separate percentage mixtures with the additive, a predetermined relationship could be expressed for each base oil. Such relationship follows a curve of the general form as illustrated in FIG. 9. This could be represented by the following equation:

3 )i=, i= i( t1) (n wherein'H, is the viscosity H-value of a given base oil-additive combination; and h,- is the viscosity l-l-value of the base oil aone; a, and b, are constants; and x, is the volume-fraction of the additive; and eis the natural log base.

Since the h, is known or can be readily determined for each base oil, the H-value of a base oil i with any volume-fraction x, of a given additive, from 0.0 to somewhat above 0.06, could be predicted by the following cquation:

These base oil-additive combinations can then be treated as separate'components in a blend, each with H-value H The viscosity l-l-value of a blend of n base oils with a given concentration x, of an additive is thus calculated by where x, (i 2, 3, n) is the volume-fraction of base oil i in the blend. The blend H-values at 100F and 210F may then be used in the Standard formula noted above to calculate a predetermined blend viscosity and viscosity index.

It will be understood, that throughout this disclosure the abbreviation Vl stands for viscosity index.

It was also discovered that the pour point of each base oil mixed with the additive would have a predetermined relationship which follows the general form similar to that for the H-value, as illustrated in FIG. 9, except that thepour point decreases with increasing additive dosage. Consequently, if the pour points of the base oil-additive mixtures using two separate percentages, e.g., with 3 and 6 percent of the additive, was also measured, such data could be converted to form a blending equation comparable to the H-value equation for viscosity.

Thus, using calculations similar to those made for viscosity, the pour blending value (PBV) of any blend of base oils with volume-fraction x, of the additive could be found by using the following equation:

where PBV is thepour blending value of a blend with volume-fraction x, of additive; (Pbv), is the pour blending value of base oil i; and where c, and d, are constants calculated for base oil 1'.

With respect to other characteristics of a blend of base oils with a VI improver additive included, such as flash point, aniline point, and ASTM color, there was found to be no significant change because of the additive. Consequently, linear blending values previously developed for such property of each base oil could be used to predetermine these characteristics of blends. The characteristic blending value of a blend containing volume-fraction x, of base all i (i 2. 3, n) could thus be found by the equation;

l "xi where BV is the characteristic blending value of a blend; (BV), is the corresponding property blending value for base oil i; and x, is the volume-fraction of th additive in the blend, as above.

The resulting expressions, e.g., (3), (4) and (5) above, allow prediction of the viscosities at l00F and 210F (and hence Vl), plus pour point, flash point. aniline point, and ASTM color of any blend of base oils with a VI improver. It is to be noted that the entire relationship of the constituents of a blend with an additive may be derived from data taken at only two additive levels for each base oil. It will be appreciated that conventional and/or stardard equipment (not shown) may be employed in carrying out the measurements of the properties. As pointed out above, the measurements are made using each of two different percentage amounts of an additive in therange from about 1 to about l0 percent mixed with each base oil individually. Actual percentage amounts of an additive that were used in carrying out the invention were 3 and 6 percent.

The entire lube oil blending procedure and system lends itself to use with a computer in order to find the minimum-cost blend which meets a given set of characteristic specifications. Using a digital computer, a skilled programmer could write a program using nonlinear constraints so as to minimize the cost function which would be expressed in the form:

C E Cm subject to contraints (i.e. specifications) expressed in forms such as the following:

The viscosity constraints H and H would be:

PBVL e bv an t en} and each additional specification would have constraints BV and BV of the form 71 BVL s 2 (Bl )1 s B Vu (9) where C is the total cost of a blend; C, is the cost of a constituent base oil 1'; and x, is the volume-fraction of base oil 1' in the blend, as in previous expressions; and where H, PBV and BV are characteristics; and the other terms used in the expressions (7), (8) and (9) are all the same as in previous expressions. Some typical specification characteristics are gravity, flash point, etc.

Referring to FIG. 1, base oils A, B and Ctrom storage facilities (not shown) are provided to a blending tank 1 through lines 2. 3 and 4.'For convenience. the following example disclosing the present invention will show the use of three base oils, although there is no restriction on the number of base oils that may be blended in tank 1 to provide a blend oil. The flow rate of a base oil is directly related to the quantity of that base oil in I the final blend oil. The flow-rate of the base oil A in line 2 is controlled by a valve 6 receiving a signal from a flow recorder controller 8, Flow recorder controller 8 receives a signal corresponding to the flow rate of base oil A in line 2 from a flow rate sensor 10. The set point of flow rate controller 8 is positioned to a desired flow rate, as hereinafter described, which will provide .the desired portion of base oil A for a desired blend oil in blending tank 1. Flow recorder controller 8 provides the signal to-valve 6 in accordance with the difference between the flow rate signal from sensor and the position of its set point so that the flow rate in line 2 as: sumes the desired flowrate;

Similarly the flow rate of base oil B in line 3 is controlled by the cooperation of a valve 6A, a flow rate sensor 10A arid a flow recorder c'ontroller, 8A. The

through E and a reset pulse E Reset pulseE occurs when counter 30 is full. Reset pulse E,,resets flip-flop 24 to a clear state thereby disabling AND gate26. When disabled AND gate 26 blocks thetirning'pulses from clock; 27 to prevent further counting by counter 30. Reset pulse E, also resets counter 30 to a zero count. Programmer 12 provides reset pulse E to other portions of thecontrol system as hereinafter disclosed.

7 provide an'inhibiting pulse'E quantity of base oil C entering tank 1 is also controlled I in a similar manner by a valve 63 and flow recorder controller 8B and a flow rate sensor 10B. Elements.

havinga number and a suffix are connected and operate in a similar manner to'those elements having the identical number without a suffix.

A viscosity impro'ver additive is also provided'to tank l through a line 11. A valve 6C, a flow recorder'con troller 8C and a sensor 10C cooperate to control the flow rate of the additive inline 11. A direct current voltageV sets the set pointin controller 10C to a position corresponding to the predetermined flow rate.

Although, for purposes of illustration, the'fiow rate of the additive and base oils are shownas being con-. trolled by flow recorder controller cooperating-valves and flow sensors, it would be obvious to one skilled in the art that the flow rates can be controlled using meters, valves, differential control counters and digital-toanalog-converters. Such a control method is discussed in an article by Mr. J. J. Jiskoot in the Oct, 1968 issue of the'Chemical and Process Engineering at page 87.

The set points of flow; recorder controllers 8, 8A and 8B are controlled in accordance with equations 6, 7, 8 and 10. In this regard, a programmer 12, which is shown in detail in FIG. 2, provides control pulses B, through E,,- to X,- signal means 14 through 14C, respectively. X, signal means 14 through 14C cooperate to provide signals E through E respectively, which correspond to the quantitiesof base oils A, B and C, and the additive, respectively, for a particular blend oil. The providing of signals E through E may also be done by various types of memory means, in which various combinations of base oils A, B and C have been stored, that would replace. programmer l2 and X, signal means 14 throughl4C;

Referring now to FIGS. 1, 2 and 3, signals E through E are developed as follows. An operator activates a switch 20 in programmer 12 receiving a direct circuit voltage V,'. Switch 20 may be a conventional type momentaryjon type of switch. Voltage V, passed by switch 20 triggers a flip-flop 24 to a set state-A flip-flop provides a high .level direct current outputwhen in a set state and a low level direct current output when in a clear state. The high level output from flip-flop 24 causes an AND gate 26 to pass timing pulsesfrom a clock 27 to a counter 30. Counter 30 counts the timing pulses and its content is decoded by a logic decoder 31 to provide a plurality of outputs to a corresponding plurality of one shot multivibrators 35. One shot multivibrators 35 provide a plurality of control pulses E FIG. 3 shows iii-detail X, signal means '14 which includes a plurality of conventional type electronic switches 40 through 40D. The number-of switches correspond tothe number of combinations of base oils-A, B and C and additive that is expected to be utilized. For example, if more base oils than base oils A, B and'C were desired for blending, then more switches are needed because there would be more possible. blend combinations of the. various base oils.

Direct current voltagesie, B through V provided.

by a conventional type direct current voltage source not shown, correspond to predetermined quantities of base oil A for different blend oils. For a countof one, electronicswitch 40 receiving voltage V 'is activated by pulse E A from programmer 14, to provide voltage V assignal E Similarly, pulse E causes signal means 14A, 14B, 14C to provide otherdirect current voltages corresponding to thequantities of base-oils B & C standard the additive necessary for that-particular blend oil 'to be providedas signals E E and E Similarly,

pulses E EC, E1; the range and E will rendegswitchgs 40A, 40C and 40D, respectively, conductive in turn to provide direct current 'voltages V through Vp respectively as base oil A quantity signal E In a similar manner signal means 14A, 14B, 14C are also controlled to provide 'corresponding'direct currentvoltages so that at any one time signals E through E correspond to quantities of base oil A, B arid C and the additive required to make a particular blend oil. Inessence, signal means 14, 14A, 14B, and 14C, along with the voltage source, comprise memory means storing signals corresponding to quantities of base oils A, B and C and the additive fordifferent blend oils.

Although a particular blend oil has been defined by signals E E and E it does not necessarily follow that the particular blend oil is acceptable or that the particular blend oil, if acceptable, is the most economical blend oil obtainable. c

Referring-to FIGS. 1, 4 and 5, control means. 42 determines if a particular blend oil, as defined by signals E E E andE 2 meets the various constraints imposedon a blend oil and more particularly the characteristics defined by equations 3, 4 and 5. Constraint control means 42 includes an H constraint circuit 44, a pour constraint circuit 45, a flash point constraint circuit 46, an aniline constraint circuit 47 and an ASTM color constraint circuit 48. Constraint circuits 44 through 48 provide a plurality of direct current outputs to an AND gate 50. Each constraint circuitjwill provide a high level output when a parameter, being monitored by the constraint circuit, is within upper and lower constraint limits and a low level output when the monitored parameter is not within the constraint limits. When all parameters are within their constraint limits, AND gate 50 provides anoutput E, at a high level output 'as signal E and a low level output as signal E when any or all of the constraint circuits outputs are at a low level.

Signals E E E E are applied to H, networks 55, 55A and 558, respectively, providing signals E E and respectively, corresponding to the H values for blend oils A, B and C, respectively. In network 55, a multiplier 56 multiplies direct current voltage V corresponding to the term k with signal E from signal means 14 to provide a signal correspondingto the term b X. The signal from multiplier 56 is applied to a unity gain inverting amplifier 57. A logarithmic amplifier 58 provides an output corresponding to the logarithm of a direct current voltage V which corresponds to the term e in equation 3. A multiplier 63 multiplies the output from amplifiers 57, 58 to provide a signal corresponding to the term b X, log e to an antilog circuit comprising an operational amplifier 64 having a function generator 65 as a feedback network. Function generator 65 may be of the type manufactuered by Electronic Associates under their Part Number PC12. Thus, the output from amplifier 64 corresponds to the term e X v The output from amplifier 64 is subtracted from a di-v rect current voltage V corresponding to the term 1 in equation 3, by subtracting means 70. A multiplier 71 multiplies the output from subtracting means 70 with a direct current voltage V corresponding to the term a Summing means 72 sums the output from multiplier 71 with a direct current voltage V corresponding to the term I1 in equation 3, to provide a signal to another multiplier 73. A divider 74 divides signal E with a signal fromsubtracting means 75 corresponding to the term 1 X,, to provide an output to multiplier 73.Subtracting means 75 subtracts signal E from voltage V Multiplier 73 multiplies the output from summing means 72 and divider 74 to provide signal E Similarly networks 55A and 55B operate on signals E E E respectively, to provide signals E and in circuit 44, summing means 80 sums signals E E and E to provide a signal E corresponding to the H value for base oil A with direct current voltages V and V corresponding to predetermined upper and lower constraint limits, respectively. Comparator 81 provides a high level output when voltageV, is more positive than signal E and a low level output when V is not more positive than signal E Comparator 81A provides a high level output when signal E is more positive than voltage V and a low level output when signal E is not morepositive than voltage V so that when H is within the constraint limits, comparators 81, 81A provide high level outputs which cause an AND gate 82 to provide a high level output to AND gate 50. When the H value exceeds the upper constraint limit, signal E is more positive than voltage V causing comparator 81 to provide a low level output which disables AND gate 82 causing it to provide a low level output to AND gate 50. Similarly, when the H value is less than the lower constraint limit signal E is not more positive than voltage V which causes comparator 81A to provide a low level output which has the same effect as when comparator 81 provided a low level output.

Pour constraint circuit 45 is similar to constraint circuit 44. Pour constraint circuit 45 utilizes PBV, networks in place of the H,- networks 55 through 55D in constraint circuit 45. The PBV, circuits are, similar to the H networks with the difference being that the direct current voltages received correspond to the constants c and d instead of a and b and the PBV, network has summing means instead of having subtracting means which sums the output from the operational amplifier with a direct current voltage corresponding to PBV,

Constraint circuits 46, 47 and 48 are identical with each other and are similar to constraint circuit 44. The difference between constraint circuits 46, 47 and 48 are constraint circuit 44 is that constraint circuit 44 uses H,- networks 55 through 558 while constraint circuits 46, 47, 48 use PV,- networks in lieu of networks 55 through 55B. Referring to FIG. 6, there is shown a BV, network. A divider 88 divides signal E with a signal from subtracting means 90. Means subtracts signal E from voltage V A multiplier 89 multiplies the signal from divider 88 with a direct current voltage V which corresponds to the blendvalue of a particular characteristic, which by way of example may be the ASTM color, for base oil A to provide a signal corresponding to a particular BV,- value.

Referring now to FIGS. 1 and 7, programmer 12 provides reset pulse E to blending control means 90 which also receives signals E E and E 3 from X; signal means 14, 14A and 14B, respectively, and signal E, from constraint control means 42. Blending control means 90 provides signals E E and E corresponding to desired set point positions for'flow recorder controllers 8, 8A and 8B, respectively,- to set their set points to control the blending of base oils A, B and C with the additive in tank 1. Multipliers 93, 93A and 93C in blending control means 90 provides signals corresponding tothe cost' for the different component portions of a particular blend oil. Multiplier 93 multiplies direct current voltages V and V corresponding to X, and C the cost of the additive, to provide a cost signal. Similarly, direct current voltages V V and V corresponding to economic values of base oils A, B and C, respectively, are multiplied with signals E E -and E respectively, by multipliers 93A, 93B and 93C, respectively, to provide cost signals. Summing means 94 sums the cost signals from multipliers 93 through 93C to provide a blend oil cost signal E corresponding to C in equation 6.

Signal E isapplied to a conventional type analog-todigital converter 98 which provides digital signals, corresponding to signal E to a plurality of AND gate 99. Signal E is also provided to AND gates 99 to partially enable those gates. When AND gates 99 receive a transfer pulse as hereinafter explained, the digital signals from converter 98 are transferred to a storage register 100.

Storage register 100 effectively stores the minimum cost signal. This is accomplished by applying outputs from storage register 100 to a conventional type digitalto-analog converter 101 which provides an analog signal E corresponding to the content of register 100. Signal E is applied to an electronic switch 107 and to a comparator 108. Electronic switch 107 is in effect a single pole double throw switch receiving a direct current voltage V Voltage V has an amplitude larger than the amplitude of a typical cost signal E Comparator 108 receives voltage V11 hich substantially corresponds to a zero value so that when the content of storage 100 is zero comparator 108 provides a high level signal to electronic switch 107. Electronic switch 107 passes voltage V to a comparator 112 when comparator 108 provides a high level signal and signal E when comparator 108 provides a low level signal.

The use of switch 107, comparator 108 and voltages V and V is necessitated by the initial condition of storage register 100. Since the object of register 100 is to store the minimum cost signal, when register 100 initially has a zero content it is impossible-to enter any cost signal into register 100 but for the operation of switch 107 and comparator 108.

An AND gate 113 controls an electronic switch 114 receiving signal E from converter 98 and direct cur rent voltage V in accordance with signal E and inhibiting pulse E Switch 114 passes signal E i and blocks voltage V when signal E is at a high level and inhibiting pulse 13,, is absent. Switch 114 blocks signal E and passes voltage V, -when signal E is at a low level or inhibiting pulse E is present. 7

Duringthe initial phase of the operation, comparator 112 goes to a low level in response to voltage V being greater'than a passed signal E from switch 114.

A one shot multivibrator ,118 is triggered by the change to a low-level in the output from comparator 112 toprovide a reset pulse to an AND gate 121 which is controlled by signal E When switch 1.14 blocks signal E i, comparator ll2outp'ut would go to a low level causing one shot multivibrator 118 to provide a reset pulse which would erroneously reset register 100 and other registers if AND gate 121 was not there. How,- ever, AND gate 121 is disabled by the low level of signal E and blocks such anerroneous pulse.

The pulse provided by one shot multivibrator 118 passes through AND gate 121 and is applied to another one shot multivibrator 119 and to register 100 through an OR gate 120. Register 100 is reset by the pulse while one shot multivibrator 119 is triggered by the trailing edge of the pulse to provide a transfer pulse to AND gates 99. AND gates 99 in responseto the transfer pulse and a high level signal E enters the digital signals.

from converter- 98 into register 100.

Now, signal 13,, from converter 101 is greater than voltage V causing the output from comparator 108 togo to a low level. The low level output from comparator 108 causes switch 107 to pass signal E to comparator 112 and to block voltage V Comparator 112 now effectively compares the present blend oil cost, as represwitch 114 to provide voltage V to comparator 112.

Since voltage'V is greater than signal E comparator 112 output goes to a high level. Now, when the next successive cost is lower than the next preceding cost, comparator 112 output will change from a high level to a low leveltriggering one shot multivibrator 118.

Where the present cost is greater than the minimum cost, comparator 112 output remains at a high level At this time, it would be appropriate to explain the effect of inhibiting pulse Eg without AND gate 113,

voltage V and inhibiting pulse E and with signal E and does not trigger one shot multivibrator 118. Since.

one shot multivibrator 118' is not triggered, the minimum cost remains stored in register 100. When all the costs for different blend oils have been computed, stor-, age register 100 will contain the minimum cost:

Concurrent wth storing of the minimum cost in register 100, it is necessary that the quantities of base oils A, B & C and the additive comprising the blend oil hav-.

ing the minimum cost be stored in registers. The pulse from one shotmultivibrator 118, passed by AND gate 121 resets a storage register 128 in set point signal means 130. Signal E is applied to a conventional type analog-to-digitalconverter 131 which provides corresponding digital signals to a plurality of transfer- AND gates 135. AND gates l35-are fullyenabled b'y the pulse provided by one shot multivibrator 119 so that Register 128 provides a plurality of outputs to transfer AND gates 140, wich are connected to'stora'ge register 141. Reset pulse E, from programmer 12 resets registers 100 and register 141. Pulse E also triggers. a one shot multivibrator 142 causing it to provide an enabling pulse to AND gates 140 causing them to transfer the content of registers 128 to 141. Register 141 holds the content corresponding to the quantity of base oil A in the minimum cost blend oil until the operation is repeated.

The signals stored in register 141 correspond to a quantity and must be converted to a flow rate control signal. A conventional digital-to-analog converter 150 converts the outputs from register 141 to an analog signal. A multiplier 151 multiplies the signal'from converter 150 with a conversion signal E to providesi'gnal E Summing means 152 sums x, through at, signals from signal means -130C, respectively, to provide a sum signal to a divider 153. Divider 153 divides a direct current voltage V with the sum signal to provide signal E I Set point signal means 130A, 1308, 130C provides signal E and E respectively, in a similar manner to that of the set point signal means 130 so that valves 6 through 6C are controlled to allow the properrates of the base oils & additive to achieve a minimum cost blend oil.

Although an analog computer has been used to describe the present invention, it would be obvious to one skilled in theart to use a general purpose digital computer so that the present invention is not restricted to an analog computer but also encompasses digital computer control as well as hybrid digital and analog control systems. Referring to FIG. 8, a general purpose digital computer provides digital outputs to digitahtoanalog converters 141-141C which converts the digital outputs to signals E through E respectively. Computer 140 is programmed in a conventional manner to provide the digital outputs as follows:

1. Store in the computer memory values for different quantities-of base oils A, B and C & the additive.

2. Store in the computer memory, equations 3 through 6.

3. Store in the computer memory, predetermined values for a, b, c, d, h, phv, ASTM color bv, flash point bv and aniline point lav for each base oil.

4. Store predetermined limits for H, PBV, ASTM color BV, flash point BV and aniline point BV.

5. Store the costs c 6;; and c of base oils A, B and C, respectively, in the memory.

6. Select a first combination of base oil and additive quantities.

7. Calculate'H using equation 3, PBV using equation 4 and the'ASTM color BV, flashpoint BV and aniline point BV using equation 6 in accordance with the selected base oils quantities values and the stored values of a, b, c, d, h, pbv, AST, color bv, flash point bv and aniline point bv.

8. Compare the calculated values of H, PBV, ASTM color BV, last point BV and aniline BV with their respective limits stored in the memory.

9. If any ofthecalculated values are not within the limits, repeat steps 6 through 8 and 9 or 10, whichever is applicable, for the next blend combination of base oil quantities.

10. If all of the calculated values are within the limits, calculate the cost of the blend combination.

1 1. If there is no'minimum cost, store the present cost and blend combination quantities values and select anext combination of blend oil quantities values and repeat steps 7 through 11. 7 12. If there be stored minimum cost, compare the present cost with the stored cost.

13. If the stored cost is less than the present cost, select a next combination of base oils quantities values and repeat steps 7 through l2.

l4. If the stored cost is not less than the present cost,

store the present cost and the blend combination quantities values associated with the present cost.

15. Select a next combination of blend oils quantities values and repeat steps 6 through 14 until all of the different combination of quantities values have been processed, at that time the digital signals corresponding to the stored values of quantities of base oils and additive are provided as the digital outputs.

The apparatus of the present invention as heretofore described controls the blending of base oils with an additive to achieve v a blend oil meeting predetermined characteristics. The apparatus also computes the cost for difference blend oils and effectively controls the blendingof the base oils and additives to achieve the blend oil meeting the predetermined specifications but also having a minimum cost. The apparatus may be an analog computer specifically arranged to solve the equations heretofore described or it may be a general purpose digital computer program to solve the equations and to provide outputs controlling the blending of the base oils and additives.

What is claimed is:

l. A system for controlling the blending of base oils and an additive, to achieve a desired blend having predetermined characteristics, being provided to blending means, comprising means for controlling the quantities of base oils and additive being provided to the blending means to be blendedin accordance with control signals, means for providing signals corresponding to the predetermined characteristics for-a desired blend of base oils and the additive, means for providing signals corresponding to the economic values of the base oils, memory means for storing values of different combinations of the base oils and the additive quantities, means connected to the value signal means, to the memory means and to the characteristic signal means for selecting a desired combination of base oil and additive quantities in accordance with the economic value signals and the characteristic signals and providing signals corresponding thereto to the control means as control signals so as to achieve the desired blend of base oils and the additive.

2. A system as described in claim 1 in which the selecting means includes means connected to the memory means for controlling the memory means 'to provide signals corresponding to quantities of base' oils &

additive for different combination thereof comprising I different blends in an iterative manner, means connected tothe-memory means and to the value signal means for providing a signal corresponding to the cost of a combination 'of the quantities represented by the signals provided by the memory means in accordance with the economic value signals and the following equation: I

where c, is the cost of a particular base oil, x, is the percent volume of the particular base oil and x is the percent volume of the additive, means connected to the characteristic signal means for determining those combinations of base oil quantities that meet the predetermined characteristics in accordance with the characteristic signals and providing a signal corresponding thereto, and output means connected'to the cost signal means, to the determining means, to the memory means and to the control means for providing the quantity signals from the memory means, corresponding to the combination of quantities of the base oilsand the additive having a minimum cost that meet the predetermine characteristics as the control signals in accordance with the determination signal and the cost signal.

3. A system as described in claim 2 in which the predetermined characteristics are the H value, the pour blend value PBV, and ASTMcolor blend value, the flash point blend value BV and the aniline point blend value and the determining means includes means receiving direct current voltages corresponding to terms h,. a and b for the different base oils and 1, associated with the following equations, and connected to the memory means for providing a signal corresponding to H for a present combination of base oils quantities in accordance with the following equation:

where h, is the H value for a base oil a, and b. are constants associated with the base oil i, and is a constant; means receiving direct current voltages corresponding to pvb, c, d, and l and connected to the memory means for providing a signal corresponding to the pour blend value PBV of the present combination of base oils quantities in accordance with the following equation:

EV i (bV where BV is the blend value of a particular characteristic such as the ASTM color, the flash point and the aniline point for the present combination of base oil quantities and bv,- is the blend value of a particular characteristic for the base oil i; and means connected to the H signal means, to the PBV signal means, to the BV signal means and to the output means and receiving direct current voltages corresponding to limits for the H value, the pour blend value PBV, the ASTM color blend value BV, the flash point blend value BV and the aniline point blend value BV for providing a signal to the output means as the determination signal having one amplitude when the H factor, the pour blend value PBV, the ASTM color blend value BV, the flash point blend value BV and the aniline point blend value BV are within their respective limits and another amplitude when at least one of the determined characteristics is not within its corresponding H 

1. A system for controlling the blending of base oils and an additive, to achieve a desired blend having predetermined characteristics, being provided to blending means, comprising means for controlling the quantities of Base oils and additive being provided to the blending means to be blended in accordance with control signals, means for providing signals corresponding to the predetermined characteristics for a desired blend of base oils and the additive, means for providing signals corresponding to the economic values of the base oils, memory means for storing values of different combinations of the base oils and the additive quantities, means connected to the value signal means, to the memory means and to the characteristic signal means for selecting a desired combination of base oil and additive quantities in accordance with the economic value signals and the characteristic signals and providing signals corresponding thereto to the control means as control signals so as to achieve the desired blend of base oils and the additive.
 2. A system as described in claim 1 in which the selecting means includes means connected to the memory means for controlling the memory means to provide signals corresponding to quantities of base oils & additive for different combination thereof comprising different blends in an iterative manner, means connected to the memory means and to the value signal means for providing a signal corresponding to the cost of a combination of the quantities represented by the signals provided by the memory means in accordance with the economic value signals and the following equation:
 3. A system as described in claim 2 in which the predetermined characteristics are the H value, the pour blend value PBV, and ASTM color blend value, the flash point blend value BV and the aniline point blend value and the determining means includes means receiving direct current voltages corresponding to terms h, a and b for the different base oils and l, associated with the following equations, and connected to the memory means for providing a signal corresponding to H for a present combination of base oils quantities in accordance with the following equation: 